UNITED NATIONS, United States (AFP) - North Korea threatened on Friday to launch a "very strong military counteraction" if South Korea refuses to halt propaganda broadcasts, in a warning delivered at the United Nations.

Pyongyang's deputy UN ambassador An Myong Hun told reporters that "if South Korea does not respond to our ultimatum, our military counteraction will be inevitable, and that counteraction will be very strong."

North Korea has put its front-line troops on combat readiness after delivering an ultimatum to South Korea to switch off its propaganda loudspeakers by Saturday afternoon or face military action.

The ultimatum came a day after a rare exchange of artillery fire that put the South Korean army on maximum alert.

North Korea has requested an urgent meeting of the Security Council to discuss the crisis, but diplomats said none of the council members had backed the request, including Pyongyang's ally China.

"The situation on the Korean Peninsula inches close to the brink of a war," An told reporters.

The deputy ambassador accused the United States and South Korea of staging "provocations" and of "fabricating" claims that North Korea was behind recent landmine explosions and shelling.

Tensions have been simmering since the landmine blasts that maimed two members of a South Korean border patrol this month and the launch Monday of a major South Korea-US military exercise that infuriated Pyongyang.

UN Secretary-General Ban Ki-moon urged North and South Korea to put a halt to the worrying escalation of tensions on the divided peninsula.

Ban, who served as South Korea's foreign minister from 2004 to 2006, said he was "deeply concerned" by the developments and called for dialogue to reduce tensions.

He "urges the parties to refrain from taking any further measures that might increase tensions," said his spokeswoman Eri Kaneko.

The 1950-53 Korean War ended in a truce but not a peace treaty, which means that the two Koreas technically remain at war.